If you have kids, better watch out for free educative apps with ads in them. Apparently, they can be a backdoor for R-rated messages about hot dating, guns and, even worse, scientology. Check out the image for a small sample.

The first case was caught by a man living in Austria. His 6-year-old son was using Nursery TV for iPhone, a nursery-rhymes app, when he asked him: "Papa, what is Scientology?" As it turns out, the app was displaying an ad proselytizing Tom Cruise's eyes wide shut club.

There have been other examples in both iOS and Android apps. They go from dating sites and gun sales to online casinos and the aforementioned Scientology. These R-rated banners are served by ad networks like Google's AdMob, which the developers use in their free apps to bring some cents in.

The only real defense against them is to buy versions of the apps without ads. [The Daily]